1. Field of the Invention
The present invention relates to a camera system, and more particularly, to a camera system including a plurality of cameras using different types of photosensitive members and a lens apparatus for use in these cameras.
2. Description of the Related Art
Photosensitive members used in cameras include films and solid-state image pickup devices such as CCDs and CMOSs. Among them, in a camera (digital still camera) using a solid-state image pickup device, especially, an image pickup device is increasingly miniaturized with the advance of semiconductor technology to reach the point where a newly appearing image pickup device has a image pickup area size of 1 inch or smaller (1 inch or smaller diagonally) and several millions of pixels (megapixels). There are various types of image pickup devices of a plurality of image pickup area sizes or a plurality of pixel sizes, and an appropriate one of those image pickup devices is selected in accordance with a particular user group or applications and used in a camera.
There exists a camera system (optical apparatus) configured such that a removable interchangeable lens apparatus is mounted on such a camera for use.
In the camera system, a common interchangeable lens can be mounted on a plurality of cameras using films as photosensitive members or on a plurality of cameras provided with different image pickup devices as photosensitive members to take pictures.
Of camera systems (camera systems) as described above, for example in a digital camera system, an image pickup device does not particularly require a reference or standardized image pickup area size, so that the image pickup area size of the image pickup device can be arbitrarily set in accordance with applications, and the pixel size of the image pickup device can also be arbitrarily set in accordance with the grade, price, and applications of the camera.
For cameras using image pickup devices with different image pickup area sizes, however, different levels of focus accuracy (in-focus accuracy) are required due to a difference in enlarging factors. Even when image pickup devices have the same image pickup area sizes, resolutions are different if they have different pixel sizes. Thus, the diameter of a permissible circle of confusion varies in focusing.
Therefore, in the aforementioned digital camera system, an image pickup device is selected for use in the camera in accordance with focus accuracy in the interchangeable lens apparatus or the diameter of a permissible circle of confusion on the image pickup surface of the image pickup device serving as a photosensitive member.
When attempts are made to increase the size or resolution of a taken image, a possible camera system (optical apparatus) is configured to use, instead of a camera provided with an image pickup device (herein referred to as “a first image pickup device”), a camera provided with an image pickup device (herein referred to as “a second image pickup device”) with different specifications from the first image pickup device, that is, a larger image pickup area size or a smaller pixel size. Similarly, for a camera using a film as a photosensitive member, a possible camera system (optical apparatus) uses a film having a higher resolution than a resolution of another film to achieve a higher resolution of a taken image.
In this case, however, the aforementioned interchangeable lens apparatus cannot be used in common to the camera using the first image pickup device, the camera using the second image pickup device, and the camera using the film as a photosensitive member.